Method of providing a clamping strap around a television display tube and implosion-free display tube manufactured by this method

ABSTRACT

An implosion-free cathode-ray tube is disclosed in which a clamping strap is provided around the envelope of the tube in proximity to the juncture of the cone and window and spacing members, such as wedge-shaped parts, are inserted between the clamping strap and the envelope to increase tension in the strap.

O Unlted States Patent 1111 [72] Inventors Willem Fokko Nienhuis; [56] Ref re e Cited Georg Arnold Willem 1860b Spakhofl, both UNITED STATES PATENTS ol Emmasingel, Eindhoven, Netherlands; Klaus Boke' Brand Am Hang, Germany 2.785,820 3/1957 V1ncent et al.

[2i] Appl. No. 851,118

[22] Filed June 18, I969 [45] Patented June 22, I971 [73] Assignee U.S. Philips Corporation New York, N.Y. Continuation of application Ser. No. 668,066, Sept. 15, 1967, now abandoned.

[54] METHOD OF PROVIDING A CLAMPING STRAP AROUND A TELEVISION DISPLAY TUBE AND IMPLOSION-FREE DISPLAY TUBE MANUFACTURED BY THIS METHOD 3220,593 ll/l965 Powell et al.

3.248.480 4/1966 l78/7.8 3,278,682 10/1966 ZZZ/2.1 (A) 3.332569 7/1967 248/74 3,220,592 11/1965 Powelletal. 220/21 FOREIGN PATENTS 3/1959 Great Britain OTHER REFERENCES German Printed Application No. 1.238.582. April I967. Primary Examiner.loseph R. Leclair Assistant Examiner-James R. Garrett Attorney-Frank R. Trifari s R 5 o METHOD OF PROVIDING A CLAMPING STRAP AROUND A TELEVISION DISPLAY TUBE AND IMPLOSION-FREE'DISPLAY TUBE MANUFACTURED BY THIS METHOD This application is a continuation of applicants prior copending application Ser. No. 668,066, filed Sept. 15, 1967, now abandoned.

The invention relates to a method of providing a clamping strap around a television tube envelope having a substantially rectangular screen, and more particularly to a method in which the strap can be stretched uniformly in a very simple manner.

Known clamping straps are generally stretched by tightening bolts or clam s. It is then inevitable that the strap, when stretched, slides over the glass with a certain amount of friction especially at the comers. It has been found that this results in a very uneven distribution of the tensile force in the strap along its periphery. In a strap having one welding joint,

'the tensile force in the part of the strap opposite this joint is found to be considerably lower than the tensile force at the said joint. However, when the ends of the strap are fixed by clamping and bending over, the tensile force in the strap is found to decrease strongly at the joint, so that ultimately the tensile force in the strap, though more uniformly distributed along the periphery, is considerably lower than the tensile force adjusted. Moreover, when steel straps are used, sliding of the strap over the glass may involve the risk of scratching the glass. After some time, such scratches may give rise to the formation of cracks through which air may leak into the tube so that the tube becomes unserviceable. Such straps of hardened steel or high-grade steel must be used if a comparatively narrow clamping strap is employed, for example, if this strap must be located entirely between the mold parting line and the sealing seam of the window.

A simple method of unifonnly stretching such a clamping strap, in which the said disadvantages are avoided, is obtained if, according to the invention, an annular strap having an inner periphery approximately equal to or larger than the outer periphery of the bulb around which the strap will be arranged, is provided around the bulb, whereupon wedge-shaped parts and, as the case may be, spacing blocks are pressed between the bulb and the strap so that the required tensile force in the strap is obtained, while steps are taken by which the strap and wedge-shaped parts are fixed to the glass. This may be achieved by roughening the surface of the strap and/or the wedges and/or the glass at the corners, but preferably by fixing the strap and the wedge-shaped parts to the glass by means of an adhesive, such as a cement, a hardening synthetic resin and the like, which may be cast, for example, into the spaces between the said parts and the glass, for it has been found necessary to ensure that the strap and/or the wedges cannot be detached from the bulb by shocks and the like.

The wedge-shaped parts preferably consist of a metal which is softer than the glass of the bulb so that there is no risk of the glass being scratched. On the other hand, the material of the wedge-shaped parts is not allowed to be deformed strongly by the large tensile force. Very suitable materials are unhardened steel and aluminum alloys. If desired, use may be made of a hard synthetic resin which may be reinforced by a suitable material or even of a hard kind of wood.

The wedge-shaped parts are preferably arranged at the center of the straight sides or are distributed uniformly over these straight sides, since the force required for inserting the wedges to obtain a given tensile force in the strap may be comparatively small. Moreover, an additional pressure is then exerted on the glass along these straight sides, which has a favorable influence on the reinforcement of the glass surface of these flat sides located between the mold parting line and the front of the window. In order to obtain a satisfactory engagement of the strap at the comers, spacing blocks may be provided at the comers between the strap and the glass surface.

When the wedge-shaped parts are provided at the center of the generally straight sides, the additional advantage is obtained that at this area the strap is spaced from the glass by a larger distance, which facilitates the casting of adhesive and filler materials. In order to prevent these materials form leaking out on the other side of the strap, a sealing layer, for example, consisting of acryl lacquer, plexigum lacquer or celluloseacetate lacquer may be applied to this side, which lacquer layer is preferably transparent and shockproof so that it at the same time protects the glass surface from damage by shocks. For this purpose, the lacquer layer may extend up to the front surface of the window.

The angle between the pressure surfaces of the wedgeshaped parts is chosen to be larger than that between the clamping strap and the glass surface, so that the angle between the wedges and the compressed state corresponds to that between the strap and the glass.

The wedge-shaped parts and spacing blocks may be manufactured by casting or injection-moulding, but they may also be folded from sheet material. In the latter case, they may be slightly elastic so that they satisfactorily match the shape of the bulb wall, which is of importance especially for the parts to be located at the comers. The wedge-shaped parts obtained by casting may be provided with incisions. Alternatively, a number of narrow wedges may be arranged closely adjacent each other.

The invention will now be described more fully with reference to the drawing, in which:

FIG. 1 is a sectional view of an angular point of the window of a tube envelope taken on the axis of the tube, and

FIG. 2 is a cross-sectional view taken on the line IIII of FIG. 1.

FIG. 3 is a sectional view of a wedge-shaped body folded out of sheet material and to be placed at a corner.

In the drawing, reference numeral I denotes the glass window of a tube envelope which is sealed at 3 to a glass cone 2.

The area at which the two parts of the mold in which the window 1 has been molded engage one another is referred to as the mold parting line 4. An annular steel strap 5, of which the inner periphery is approximately equal to or larger than the outer periphery of the window at the mold parting line 4, is arranged around the cone 2 at an area at which the periphery of the cone 2 is so much smaller than the inner periphery of the strap that the wedge-shaped parts and 6 which in this case are provided at the corners and along the straight sides of the envelope, can be slipped between the bulb and the strap without the strap being tautly stretched, if the wedges 6 already occupy the correct positions with respect to the strap 5. Subsequently, the wedges 6 and hence also the strap 5 are pressed over the bulb surface in the direction of the picture surface until the desired position of the strap on the bulb has been attained, the strap being stretched in the desired manner due to the larger cross section of the bulb at this area. Thus, the wedges 6 need not slide over the inner surface of the strap. The strap 5 may be made of unhardened steel and the tensile force may be so large that the limit of flow of the material of the strap is exceeded. The tensile force then always has approximately the same value independently of the tolerances of the bulb or the wedge-shaped parts of the periphery of the strap. Only the width of the strap still influences the tensile force, but the tolerances of the width of the strap may be small.

The wedge-shaped parts may taper at one end or at both ends, while gaps 7 may be provided in order to render these wedge-shaped parts slightly elastic so that they more satisfactorily engage the glass wall of the bulb. In order to prevent the strap and/or the wedges from being detached, these parts must be fixed to the glass by means of an adhesive 8 preferably consisting of a suitable hardening substance. For the purpose, the adhesive may be cast into the gap between the strap and the bulb. The strap, sealing layer 9 may have one or more indentures on the straight sides which bear on the glass and space the strap at these areas by a certain distance from the glass, which facilitates the casting process.

The wedge-shaped part of FIG. 3 is folded out of sheet material. The spacing blocks disposed at the corners or the wedge-shaped parts may also be provided with securing lugs (not shown). However, these lugs may also be secured to the strap 5 or be clamped between the strap and the wedges.

The strap 5 and the wedges 6 are preferably not arranged until the tube has otherwise been completely finished so that the strap ought not to be strongly heated. For this could result in a decrease of the tensile stress. Due to the fact that the strap is not stretched by tightening two ends and need not slide over the glass in its longitudinal direction, the tensile force is uniformly distributed along the periphery of the strap and the strap exerts a pressure on the glass which is substantially symmetrically distributed along the periphery of the bulb.

We claim: 7

l. A television tube envelope comprising a cone portion joined to a generally rectangular window portion, said window portion having an integral rearwardly extending peripheral flange, the radially outer surface of said flange having a mold parting line extending peripherally around same and parallel to the front surface of said window portion, said flange surface tapering rearwardly from said mold parting line to the rear edge of the flange, a clamping strap surrounding said envelope in proximity to said mold parting line, said clamping strap having a periphery at least as large as that of said envelope window portion, wedge-shaped members having opposite surfaces in contact with said envelope window portion flange and said clamping strap, said wedge-shaped members being disposed between said flange and strap and having a thickness which displaces the clamping strap outwardly at the positions of the wedge-shaped members thereby placing said clamping strap under tensile stress, and an adhesive material securing one of said, strap and said wedge-shaped members to said envelope.

2. A television tube envelope as claimed in claim 1 in which the wedge-shaped members are disposed between the envelope and the clamping strap intermediate the ends of the generally straight sides of the envelope window portion.

3. A television tube envelope as claimed in claim 1 which the wedge-shaped members are disposed between the corners of the envelope and the clamping strap.

4. A television tube envelope as claimed in claim 1 in which the strap is hardened steel and is disposed entirely on the side of the mold parting line adjoining the cone portion.

5. A television tube envelope as claimed in claim 1 in which the adhesive material is in the form of a layer that extends up to the window.

UNITED STATES PATENT OFFICE 5 CERTIFICATE 0F CORRECTION Patent 3.586 l99 Dated June 22. 197].

Inventor(s) It is certified that error appears in the above'identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 45, after "parts" insert 6- line 70, change first "the" to -thisline 71, after "adhesive" insert -8-- line 72, after "bulb" insert --as shown in Fig. 2-

Signed and sealed this 2! st day of December 1971 (SEAL) Attest:

E WARD M.FLETCHER,JR. ROBERT GOTTSGHALK A eating Officer Acting Commissioner of Patents 

1. A television tube envelope comprising a cone portion joined to a generally rectangular window portion, said window portion having an integral rearwardly extending peripheral flange, the radially outer surface of said flange having a mold parting line extending peripherally around same and parallel to the front surface of said window portion, said flange surface tapering rearwardly from said mold parting line to the rear edge of the flange, a clamping strap surrounding said envelope in proximity to said mold parting line, said clamping strap having a periphery at least as large as that of said envelope window portion, wedgeshaped members having opposite surfaces in contact with said envelope window portion flange and said clamping strap, said wedge-shaped members being disposed between said flange and strap and having a thickness which displaces the clamping strap outwardly at the positions of the wedge-shaped members thereby placing said clamping strap under tensile stress, and an adhesive material securing one of said, strap and said wedge-shaped members to said envelope.
 2. A television tube envelope as claimed in claim 1 in which the wedge-shaped members are disposed between the envelope and the clamping strap intermediate the ends of the generally straight sides of the envelope window portion.
 3. A television tube envelope as claimed in claim 1 which the wedge-shaped members are disposed between the corners of the envelope and the clamping strap.
 4. A television tube envelope as claimed in claim 1 in which the strap is hardened steel and is disposed entirely on the side of the Mold parting line adjoining the cone portion.
 5. A television tube envelope as claimed in claim 1 in which the adhesive material is in the form of a layer that extends up to the window. 